1. Field of the Invention
This invention relates to a cutter drum assembly for use on a boring type mining machine and, more particularly to a cutter drum having extensible end drums for expanding the cutting width of the cutter drum to dislodge solid material left uncut by the rotor cutter arms from a mine face at the mine roof and floor.
2. Description of Related Art
Related boring machines for underground mining operations typically utilize parallel interlaced rotor arms having cutting elements which cut a generally oval-shaped entry in the mine. Cutter chains or continuous cutter drums are utilized at the roof and floor levels to trim or eliminate cusps left in place because they are out of the cutting paths of the rotor arms. The cutter chain or drum at the mine floor is also used to increase the width of the cut in the mine entry.
To facilitate tramming of the machine into and out of position opposite of the mine face, the lower cutter chain or drum is retracted out of contact with the mine sidewalls and raised out of contact with the mine floor. The upper cutter chain or drum is lowered out of contact with the mine roof.
Other related boring machines also increase the width of the cut at the mine floor beyond the cutting path of the rotor arms by extending the width of the lower cutter drum once its lowered into position on the mine floor at the base of the mine face, e.g., extending the length of a cutter drum assembly on continuous mining machines.
Related continuous mining machines also have a cutter drum assembly that is rotatably mounted on a forwardly extending boom member. Pluralities of cutter bits extend outwardly from the drum member. The drum member includes intermediate drum sections and a pair of end drum sections. The intermediate and end drum sections are telescopically mounted to extend the length of the drum assembly beyond the width of the machine. Extension of the end drum sections is accomplished by lateral movement of a boom member having arm members that rotatably support end drum sections. The lateral movement is generated by hydraulic piston cylinder assemblies that exert lateral pressure on the boom arms.
Another related continuous mining machine has a forwardly extending boom assembly that is pivotally secured to the frame of the mining machine. The boom assembly includes a pair of parallel forwardly extending arm members that are pivotally connected to the mining machine body portion. A pair of parallel support members is movably secured to and extends laterally from the respective arm members. A cutter drum is rotatably supported at the forward end portions of the support members. A pair of cylinder assemblies is secured to respective arm members and each includes an extensible cylinder rod secured to a support member. Actuating the cylinder assemblies extends the end drum sections laterally away from an intermediate drum section. The end drum sections are independently extendable to increase gathering efficiency.
According to related dual rotor boring machines, a lower cutter drum assembly trims material at the mine floor left uncut by the rotor arms. Typically, the cutter drum includes a center or intermediate drum section and a pair of end drum sections separated from the intermediate drum section by gear cases. The gear cases rotatably support the respective cutter drum sections.
According to one dual rotor assembly, each gear case is positioned below and centered on a rotor axis. With this arrangement, when the end drums are extended to increase the length of the lower cutter drum to increase the width of cut, gaps are formed in the cutting paths between the extended end drums and the rotor arms. This leaves uncut material or cusps projecting upwardly from the mine floor at the mine face.
A typical arrangement of these related machines includes a cutter drum section having a fixed portion and an outer extensible portion. The outer extensible portion is supported by and telescopically extends from an outboard end of the fixed portion to increase the width of cut. However, this places additional loads, e.g., bending moments, at the outboard end of the fixed portion. It is believed that the telescopic overlap of the extensible and fixed portions that is necessary to accommodate these additional loads in the extended configuration is at least 1.5 times the telescopic diameter. Moreover, the bearings and structures that support the whole cutter drum section must be made more robust to account for these additional loads.
While it is known to extend the length of a cutter drum assembly on a continuous mining machine, there is a need for an extensible cutter drum assembly on a boring type mining machine that separates the forces required for transferring torque and for extending/retracting an extension drum with respect to a main drum. In particular, there is a need for the extension drum of a lower cutter drum assembly to be supported independently of the main drum for relative extension and retraction.